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Inclusive dijet production at low Bjorken-x in deep inelastic scattering
(2004)The European Physical Journal CDijet production in deep inelastic ep scattering is investigated in the region of low values of the Bjorken-variable x (10-4 < x < 10-2) and low photon virtualities Q 2 (5 < Q 2 < 100 GeV2). The measured dijet cross sections are compared with perturbative QCD calculations in next-to-leading order. For most dijet variables studied, these calculations can provide a reasonable description of the data over the full phase space region covered, ...Journal Article -
Measurement of prompt photon cross sections in photoproduction at HERA
(2005)The European Physical Journal CResults are presented on the photoproduction of isolated prompt photons, inclusively and associated with jets, in the γp center of mass energy range 142 < W < 266 GeV. The cross sections are measured for the transverse momentum range of the photons 5<EγT<10 GeV and for associated jets with E T jet > 4.5 GeV. They are measured differentially as a function of EγT,EjetT, the pseudorapidities ηγ and ηjet and estimators of the momentum fractions ...Journal Article -
Fermion pair production in e+e- collisions at 189-209 GeV and constraints on physics beyond the standard model
(2007)The European Physical Journal CCross sections, angular distributions and forward-backward asymmetries are presented, of two-fermion events produced in e+e- collisions at centre-of-mass energies from 189 to 209 GeV at LEP, measured with the ALEPH detector. Results for e+e-, μ+μ-, τ+τ-, qq̄, bb̄ and cc̄ production are in agreement with the standard model predictions. Constraints are set on scenarios of new physics such as four-fermion contact interactions, leptoquarks, ...Journal Article -
Study of spin and decay-plane correlations of W bosons in the e(+) e(-)-> W+W- process at LEP
(2005)The European Physical Journal CData collected at LEP at centre-of-mass energies s√=189−209 GeV are used to study correlations of the spin of W bosons using e+e−→W+W−→\ensuremathℓνqq¯ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e−→W+W−→\ensuremathℓνqq¯ and e+e−→W+W−→\ensuremathqq¯qq¯ events. Decay-plane correlations are measured to be ...Journal Article -
Measurement of F-2(c(c)over-bar) and F-2(b(b)over-bar) at high Q(2) using the H1 vertex detector at HERA
(2005)The European Physical Journal CMeasurements are presented of inclusive charm and beauty cross sections in e + p collisions at HERA for values of photon virtuality Q 2 > 150 GeV2 and of inelasticity 0.1 < y < 0.7. The charm and beauty fractions are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. The data are divided into four regions in Q 2 and Bjorken x, and values ...Journal Article -
Single- and multi-photon production in e(+) e(-) collisions at √s up to 209 GeV
(2003)The European Physical Journal CEvents containing only energetic photons are analysed in a sample of 628pb−1 of data recorded from e+e− collisions at centre-of-mass energies between 189 and 209 GeV by the ALEPH detector at LEP. The e+e−→νν¯γ(γ) and e+e−→γγ(γ) cross sections are measured and found to be in agreement with the standard model predictions. The number of light neutrino generations is determined to be Nν=2.86±0.09. Upper limits are derived on the cross sections ...Journal Article -
Collider aspects of flavor physics at high Q
(2008)The European Physical Journal CThis chapter of the “Flavor in the era of LHC” workshop report discusses flavor-related issues in the production and decays of heavy states at the LHC at high momentum transfer Q, both from the experimental and the theoretical perspective. We review top quark physics, and discuss the flavor aspects of several extensions of the standard model, such as supersymmetry, little Higgs models or models with extra dimensions. This includes discovery ...Journal Article -
Search for supersymmetric particles with R-parity violating decays in e(+)e(-) collisions at root s up to 209 GeV
(2003)The European Physical Journal CSearches for the pair production of supersymmetric particles under the assumption that R-parity is violated via a single dominant \ensuremathLLE¯, \ensuremathLQD¯ or \ensuremathU¯D¯D¯ coupling are performed using the data collected by the ALEPH detector at LEP at centre-of-mass energies from 189 to 209GeV. The numbers of observed candidate events in the data are in agreement with the Standard Model expectation, and limits on the production ...Journal Article -
Measurement of the hadronic photon structure function F-2(gamma)(x,Q(2)) in two-photon collisions at LEP
(2003)The European Physical Journal CThe hadronic photon structure function Fγ2(x,Q2) is measured from data taken with the ALEPH detector at LEP. At centre-of-mass energies between s√=189GeV and 207GeV an integrated luminosity of 548.4pb−1 is analyzed in two ranges of Q2 with ⟨Q2⟩=17.3 GeV2 and 67.2 GeV2. Detector effects and acceptance are corrected for with a Tikhonov unfolding procedure. The results are compared to theoretical predictions and measurements from other experiments.Journal Article -
Two-dimensional analysis of Bose-Einstein correlations in hadronic Z decays at LEP
(2004)The European Physical Journal CBose-Einstein correlations are studied in pairs of charged pions from hadronic Z decays, collected by the ALEPH detector. The correlation function, measured using either the unlike-sign or the mixed reference sample, is studied in terms of the Lorentz-invariant four-momentum difference and its transverse, Q T, and longitudinal, Q L, components with respect to the longitudinal centre-of-mass system. Values for the correlation radii, R T ...Journal Article